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Practice Questions (Short Answer)

Short Answer Questions

Question 1. Name the following
(a) The process in plants that links light energy with chemical energy
(b) Organisms that can prepare their own food
(c) The cell organelle where photosynthesis occurs
(d) Cells that surround a stomatal pore
(e) Organisms that cannot prepare their own food
(f) An enzyme secreted from gastric glands in stomach that acts on proteins.

Question 2. “All plants give out oxygen during day and carbon dioxide during night”. Do you agree with this statement? Give reason.

Answer 2. During day time, as the rate of photosynthesis is more than the rate of respiration, the net result is evolution of oxygen. At night there is no photosynthesis, so they give out carbon dioxide due to respiration.

Question 3. How do the guard cells regulate opening and closing of stomatal pores?

Answer 3. The swelling of guard cells due to absorption of water causes opening of stomatal pores while shrinking of guard cells closes the pores. Opening and closing of stomata occurs due to turgor changes in guard cells. When guard cells are turgid, stomatal pore is open while in flaccid conditions, the stomatal aperture closes.

Question 4. Two green plants are kept separately in oxygen free containers, one in the dark and the other in continuous light. Which one will live longer? Give reasons.

Answer 4. . Plant kept in continuous light will live longer, because it will be able to produce oxygen required for its respiration by the process of photosynthesis.

Question 5. If a plant is releasing carbon dioxide and taking in oxygen during the day, does it mean that there is no photosynthesis occurring? Justify your answer.

Answer 5. Release of CO2 and intake of O2 gives evidence that either photosynthesis is not taking place or its rate is too low. Normally during day time, the rate of photosynthesis is much more than the rate of respiration. So, CO2 produced during respiration is used up for photosynthesis hence CO2 is not released.

Question 6. Why do fishes die when taken out of water?

Answer 6. Fishes respire with the help of gills. Gills are richly supplied with blood capillaries and can readily absorb oxygen dissolved in water. Since fishes cannot absorb gaseous oxygen they die soon after they are taken out of water.

Question 7. Differentiate between an autotroph and a heterotroph.

Answer 7.

Autotroph Heterotroph

1. Organisms that prepare their own food. 1. Organisms that are dependent on other organisms for food.
2. They have chlorophyll. 2. They lack chlorophyll.

Question 8. Is ‘nutrition’ a necessity for an organism? Discuss.

Answer 8. Food is required for the following purposes
(a) It provides energy for the various metabolic processes in the body.
(b) It is essential for the growth of new cells and repair or replacement of worn out cells.
(c) It is needed to develop resistance against various diseases.

Question 9. What would happen if green plants disappear from earth?

Answer 9. Green plants are the sources of energy for all organisms. If all green plants disappear from the earth, all the herbivores will die due to starvation and so will the carnivores.

Question 10. Leaves of a healthy potted plant were coated with vaseline. Will this plant remain healthy for long? Give reasons for your answer.

Answer 10. This plant will not remain healthy for a long time because
(a) it will not get oxygen for respiration.
(b) it will not get carbon dioxide for photosynthesis.
(c) Upward movement of water and minerals would be hampered due to lack of transpiration.

Question 11. How does aerobic respiration differ from anaerobic respiration?

Answer 11.

Aerobic respiration Anaerobic respiration

1. Oxygen is utilised for the breakdown of respiratory 1. Oxygen is not required.
substrate.
2. It takes place in cytoplasm (glycolysis) and inside 2. It takes place in cytoplasm only.
mitochondria (Krebs cycle)
3. End products are carbon dioxide and water 3. End products are lactic acid mor ethanol and carbon dioxide.
4. More energy is released. 4. Less energy is released.